Polymerization in the presence of a β-substituted nitroxide radical

ABSTRACT

The invention relates to a process for the polymerization or copolymerization of at least one monomer which is polymerizable by the radical route in the presence of a stable free radical from the nitroxide family. The stable free radical is β-substituted and provides excellent control of polydispersity while ensuring a better rate of polymerization or copolymerization, if they are compared with the stable free radicals used in the prior art.

TECHNICAL FIELD

The invention relates to a process for the polymerization orcopolymerization of at least one monomer which is polymerizable by theradical route in the presence of a stable free radical of the nitroxidefamily.

PRIOR ART

The presence of a stable free radical during the polymerization orcopolymerization of monomers provides for control of polymerization andresults in polymers of narrower polydispersity.

The quality of a polymerization or copolymerization control can also beassessed by observation of the increase in the number-average molecularmass as a function of the percentage of conversion of the monomers topolymer or copolymer. When control is good, the number-average molecularmass is linearly proportional to the percentage of conversion. Thegreater the departure from linearity, the less good the control.

U.S. Pat. No. 4,581,429 describes a process for the manufacture ofoligomers at low temperature and with low degrees of conversion whichmakes use of a compound of formula ═N—O—X in the polymerization mixture.

U.S. Pat. No. 5,322,912 and U.S. Pat. No. 5,401,804 illustrate theeffect of stable free radicals on the polymerization of styrene. U.S.Pat. No. 5,412,047 illustrates the effect of stable free radicals on thepolymerization of acrylates. U.S. Pat. No. 5,449,724 illustrates theeffect of stable free radicals on the polymerization of ethylene. Thedocuments which have just been cited mention, as stable free radicals,cyclic molecules which have a group of low molecular mass in theposition B to the nitrogen atom of the nitroxide group, which moleculeshave in particular the disadvantage of greatly slowing down the rate ofpolymerization or copolymerization, so that it is sometimes difficult,or indeed impossible, to carry out this polymerization orcopolymerization at a temperature which is sufficiently low for thepolydispersity of the final polymer to be sufficiently narrow.

Indeed, the greater the temperature of the mixture, the poorer thecontrol of the polymerization or copolymerization, so that the finalpolymer or copolymer exhibits a higher polydispersity.

STATEMENT OF THE INVENTION

The invention overcomes the disadvantages mentioned above. The stablefree radicals introduced in the context of the present invention provideexcellent control of polydispersity while ensuring a better rate ofpolymerization or copolymerization, if they are compared with the stablefree radicals made use of by the prior art.

Another advantage of the invention is to make possible the preparationof block copolymers. Indeed, the polymerization of a first monomer inthe presence of a stable free radical results in a living polymer block.It is then possible to join a block of another polymer to this firstblock by placing the first living polymer block in a polymerizationmixture of a second monomer. It is thus possible to produce blockcopolymers, for example copolymers comprising one or a number ofpolystyrene blocks and one or a number of polybutadiene blocks. Thepreparation of such copolymers is usually very difficult by the radicalroutes of the prior art and, for their preparation, copolymerizationprocesses by the anionic route are generally resorted to.

The production of such copolymers by the radical route requires goodcontrol of the polymerization of each of the blocks. Indeed, if atermination reaction interrupts the growth by polymerization of a block,it will not be possible to join to it a block of another monomer.Termination reactions must therefore be as infrequent as possible. Thereare fewer termination reactions when, during polymerization, thenumber-average molecular mass is more linearly proportional to thepercentage of conversion. The existence of termination reactions isreflected by a decrease in the rate of increase in the number-averagemolecular mass as a function of the percentage of conversion.

The invention relates to the polymerization or copolymerization of atleast one monomer which is polymerizable in the presence of a stablefree radical from the nitroxide family comprising a sequence of formula:

in which the R_(L) radical has a molar mass greater than 15. Themonovalent R_(L) radical is said to be in the β position with respect tothe nitrogen atom of the nitroxide radical. The remaining valencies ofthe carbon atom and of the nitrogen atom in the formula (1) can bebonded to various radicals such as a hydrogen atom or a hydrocarbonradical, such as an alkyl, aryl or aralkyl radical, comprising from 1 to10 carbon atoms. It is not excluded for the carbon atom and the nitrogenatom in the formula (1) to be connected to one another via a bivalentradical, so as to form a ring. However, the remaining valencies of thecarbon atom and of the nitrogen atom of the formula (1) are preferablybonded to monovalent radicals. The R_(L) radical preferably has a molarmass greater than 30. The R_(L) radical can, for example, have a molarmass of between 40 and 450. The radical R_(L) can, by way of example, bea radical comprising a phosphoryl group, it being possible for the saidR_(L) radical to be represented by the formula:

in which R¹ and R², which can be identical or different, can be chosenfrom alkyl, cycloalkyl, alkoxy, aryloxy, aryl, aralkyloxy,perfluoroalkyl and aralkyl radicals and can comprise from one to 20carbon atoms. R¹ and/or R² can also be a halogen atom, such as achlorine or bromine or fluorine or iodine atom. The R_(L) radical canalso comprise at least one aromatic ring, such as the phenyl radical orthe naphthyl radical, it being possible for the latter to besubstituted, for example by an alkyl radical comprising from one to fourcarbon atoms.

By way of example, the stable free radical can be chosen from thefollowing list:

tert-butyl 1-phenyl-2-methylpropyl nitroxide,

tert-butyl 1-(2-naphthyl)-2-methylpropyl nitroxide,

tert-butyl 1-diethylphosphono-2,2-dimethylpropyl nitroxide,

tert-butyl 1-dibenzylphosphono-2,2-dimethylpropyl nitroxide,

phenyl 1-diethylphosphono-2,2-dimethylpropyl nitroxide,

phenyl 1-diethylphosphono-1-methylethyl nitroxide,

1-phenyl-2-methylpropyl 1-diethylphosphono-1 -methylethyl nitroxide.

The stable free radical can be introduced into the polymerization orcopolymerization mixture in the proportion of 0.005% to 5% by weight ofthe sum of the mass of polymerizable monomer and of stable free radical.

Within the context of the present invention, any monomer exhibiting acarbon-carbon double bond capable of polymerizing or copolymerizing bythe radical route can be used.

At least one monomer present in the polymerization or copolymerizationmedium can be a vinylaromatic monomer or an olefin or a diene or anacrylic or methacrylic monomer. The monomer can also be vinylidenedifluoride or vinyl chloride.

Vinylaromatic monomer is understood to mean styrene, styrene substitutedon the vinyl group by an alkyl group, such as alpha-methylstyrene, orortho-vinyltoluene, para-vinyltoluene, ortho-ethylstyrene or2,4-dimethylstyrene, or styrene substituted on the ring by a halogen,such as for example 2,4-dichlorostyrene, as well as vinylanthracene.

Diene is understood to mean in particular a conjugated diene comprisingfrom 4 to 8 carbon atoms, such as 1,3-butadiene, isoprene,2,3-dimethyl-1,3-butadiene or piperylene.

The process according to the invention is more particularly effective inthe case of vinylaromatic monomers and dienes.

The polymerization or copolymerization is carried out under the usualconditions known to the person skilled in the art, taking into accountthe monomer or monomers under consideration, since this polymerizationor copolymerization takes place by a radical mechanism, with thedifference that the β-substituted stable free radical in accordance withthe invention is added to the mixture. Depending on the nature of themonomer or monomers which it is desired to polymerize or copolymerize,it may be necessary to introduce a free-radical initiator into thepolymerization or copolymerization mixture. The person skilled in theart knows the monomers which require the presence of such an initiatorfor this monomer to polymerize or copolymerize. For example, thepolymerization or copolymerization of a diene requires the presence of afree-radical initiator.

The free-radical initiator can be introduced into the polymerization orcopolymerization mixture in the proportion of 50 to 50,000 ppm based onthe mass of polymerizable or copolymerizable monomer.

The free-radical initiator can be, for example, chosen from those ofperoxide type or of azo type. Mention may be made, by way of example, ofthe following initiators: benzoyl peroxide, lauroyl peroxide, tert-butylperacetate, tert-amyl perpivalate, butyl per-2-ethylhexanoate,tert-butyl perpivalate,tert-butyl perneodecanoate, tert-butylperisononanoate, tert-amyl perneodecanoate, tert-butyl perbenzoate,di-2-ethylhexyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, cumylperneodecanoate, tert-butyl permaleate, 2,2′-azobis(isobutyronitrile),2,2′-azobis(2,4-dimethylvaleronitrile),2,2′-azobis(cyclohexanecarbonitrile), 2,2′-azobis(2-methylbutyronitrile) and2,2′-azobis(2,4-dimethyl-4-methoxyvaleronitrile).

In the case where the mixture comprises a vinylaromatic monomer andwhere excellent control of the growth of the polymer or copolymer isdesired, so that the latter has a particularly narrow polydispersity, itis preferable to carry out the polymerization or copolymerization at atemperature at which no polymerization or copolymerization is observedin the absence of free-radical initiator and to add a free-radicalinitiator to the mixture. For example, in the case of the polymerizationor copolymerization of at least one vinylaromatic monomer, thissituation exists when the temperature is less than approximately 120° C.Appreciable polymerization or copolymerization rates are neverthelessobtained by the process of the invention when the temperature is between90 and 120° C., for example between 100 and 120° C., and when afree-radical initiator has been added to the mixture.

Nevertheless, if a higher polydispersity is accepted, heating themixture to higher temperatures is not excluded.

Thus, in the case where the mixture comprises a vinylaromatic monomer,the polymerization or copolymerization can be initiated thermally andwithout free-radical initiator, in which case it is generally carriedout between 120 and 200° C. and preferably between 120 and 160° C. If afree-radical initiator has been introduced, it is possible to carry outthe polymerization or copolymerization between 25 and 120° C. but it isalso possible, depending on the nature of the initiator and inparticular its half-life temperature, to heat to 200° C., if a greaterrate of polymerization is preferred to the detriment of thepolydispersity.

In the case where the mixture comprises a vinylaromatic monomer, thepolymerization or copolymerization can be carried out in bulk, insuspension or in solution.

In the case of a diene, the polymerization or copolymerization isgenerally carried out in solution or suspension. The polymerization orcopolymerization mixture may be intended to result in a high-impactvinylaromatic polymer, in which case it generally comprises at least onevinylaromatic monomer and one rubber, the latter generally being aconjugated polydiene such as one or a number of polybutadienes.

The invention also relates to the preparation of copolymers. Forexample, when at least one vinylaromatic monomer is present in themixture, this monomer can be copolymerized with, for example, at leastone monomer chosen from acrylonitrile, methacrylonitrile, acrylic acid,methacrylic acid, an alkyl ester in which the alkyl group contains from1 to 4 carbon atoms, an N-alkylmaleimide in which the alkyl groupcontains from 1 to 4 carbon atoms, or N-phenylmaleimide.

Of course, depending on the polymerization or copolymerizationconditions, and in particular the duration, the temperature and thedegree of conversion of monomer to polymer or copolymer, it is possibleto produce products of very different molecular masses.

The invention relates both to the preparation of oligomers, polymers orcopolymers with a weight-average molecular mass of less than 10,000gram/mol and to that of polymers or copolymers with a weight-averagemolecular mass greater than 10,000, gram/mol such as high polymers witha weight-average molecular mass generally ranging from 100,000 gram/molto 400,000 gram/mol.

The invention relates both to polymerization or copolymerizationprocesses in which the degree of conversion of monomer to polymer orcopolymer is less than 50% and to those in which the degree ofconversion of monomer to polymer or copolymer is greater than 50%.

The process for the preparation of the secondary amine can comprise astage of reaction between:

a compound C comprising a carbonyl group,

a primary amine,

a phosphorus-containing derivative comprising a phosphoryl group.

The compound C can, for example, be represented by the formula

in which R³ and R₄, which can be identical or different, can representvarious radicals such as a hydrogen atom or an alkyl, aryl or aralkylradical comprising, for example, from 1 to 10 carbon atoms. The R³ andR⁴ radicals can also be joined to one another so as to form a ring whichincludes the carbon atom of the carbonyl group. The compound C can bechosen from aldehydes or ketones.

By way of example, the compound C can be:

trimethylacetaldehyde,

isobutyraldehyde,

diethyl ketone,

dibutyl ketone,

methyl ethyl ketone,

cyclohexanone,

4-tert-butylcyclohexanone,

tetralone.

The primary amine can be represented by the formula R⁵—NH₂ in which R⁵can represent, for example, a saturated or unsaturated, linear orbranched hydrocarbon radical which can comprise at least one ring, thesaid radical comprising from 1 to 30 carbon atoms, such as an alkyl,aryl or aralkyl radical. By way of example, the R⁵ radical can be chosenfrom the following radicals: methyl, ethyl, propyl, isopropyl,tert-butyl, diphenylmethyl, triphenylmethyl, phenyl, naphthyl, benzyl or1-phenylethyl.

The phosphorus-containing derivative can be represented by the formulaHP(O)(R⁶)(R⁷) in which R⁶ and R⁷, which can be identical or different,can be chosen from alkyl, cycloalkyl, alkoxy, aryloxy, aryl, aralkyloxy,perfluoroalkyl or aralkyl radicals and can comprise from one to 20carbon atoms. R⁶ and/or R⁷ can also be a halogen atom, such as achlorine or bromine or fluorine or iodine atom. By way of example, theR⁶ and R⁷ radicals can be chosen from the following radicals: methyl,ethyl, n-propyl, isopropyl, tert-butyl, n-butyl, phenyl, benzyl,methoxy, ethoxy, trifluoromethyl or benzyloxy.

By way of example, the phosphorus-containing derivative can be: diethylphosphonate, dibenzyl phosphonate, diisopropyl phosphonate, di-n-dodecylphosphonate, diphenylphosphine oxide or dibenzylphosphine oxide.

In the reaction, the compound C and the primary amine are preferablyfirst of all brought into contact and then, in a second step, thephosphorus-containing derivative is added.

The reaction stage can be carried out, for example, between 0 and 100°C. and preferably between 20 and 60° C.

The molar ratio of the phosphorus-containing derivative to the compoundC is preferably greater than 1.

The molar ratio of the compound C to the primary amine preferably rangesfrom 0.8 to 1.5.

Following the reaction stage, the mixture contains a secondary amine,which is also the subject of the present invention. This secondary aminecan, if necessary, be isolated in any suitable way.

In particular, the mixture can be acidified by an aqueous hydrochloricacid solution in order to form a hydrochloride of the secondary amine,an organic solvent, such as an ether, can then be added to the mixturein order to dissolve the species to be removed, the aqueous phase canthen be isolated and then sodium carbonate can be added to this aqueousphase in order to release the secondary amine. The latter is thenextracted by an organic solvent, such as an ether, to be subsequentlyisolated after evaporation of the solvent.

The secondary amine can be represented by the formula:

in which the R³, R⁴, R⁵, R⁶ and R⁷ radicals retain the meanings givenabove.

The secondary amine can be used for the preparation of a nitroxide.

The process for the preparation of this nitroxide comprises, afterformation of the secondary amine, a stage of oxidation of this secondaryamine which is capable of replacing its >N—H group by an >N—O group. Anon-exhaustive list is given below of a number of suitable techniques:

reaction of the secondary amine with hydrogen peroxide, the principle ofwhich is taught by Patent Application EP 0,488,403;

reaction of the secondary amine with dimethyldioxirane according to theprinciple taught in R. W. Murray and M. Singh, Tetrahedron Letters,1988, 29(37), 4677-4680 (or U.S. Pat. No. 5,087,752);

reaction of the secondary amine with metachloroperbenzoic acid (MCPBA),according to the principle taught in J. Am. Chem. Soc., 1967, 89(12),3055-3056.

The techniques described in Patent Applications EP 0,157,738 and GB1,199,351 can also be used.

As regards the method of oxidation with MCPBA, it is preferable to carryout the oxidation under the following conditions:

molar ratio of the secondary amine to MCPBA of between 0.5 and 1 andmore preferably between 0.8 and 1;

temperature of between −10 and 10° C.,

use of an inert solvent so as to be able to exert better control overthe exothermicity of the reaction. This solvent can, for example, bechosen from the family of chlorinated solvents, such as dichloromethaneor chloroform.

The nitroxide can be represented by the formula:

in which the R³, R⁴, R⁵, R⁶ and R⁷ radicals retain the meanings givenabove. Following this stage of oxidation with MCPBA, the nitroxide canbe purified, for example by elution on a silica column, and thenisolated after evaporation of the solvents which may be necessary.

WAYS OF IMPLEMENTING THE INVENTION

The meanings of several abbreviations used in the examples are givenbelow:

Benz. Per.: Benzoyl peroxide

AIBN: 2,2′-azobis(isobutyronitrile)

Tempo: 2,2,6,6-tetramethyl-1-piperidinyloxy

DTBN: di-tert-butyl nitroxide

EXAMPLE 1

a) Synthesis of Diethyl2,2-dimethyl-1-(1,1-dimethylethylamino)propylphosphonate

6,68 g (0.077 mol) of pivaldehyde and 5.62 g (0.077 mol) oftert-butylamine are mixed at room temperature under a nitrogenatmosphere in a 250 ml, round-bottomed, two-necked flask equipped with amagnetic stirrer and a dropping funnel. The mixture is then brought to30° C. for one hour. After returning to room temperature, 26.23 g (0.19mol) of diethyl phosphonate are added dropwise to the mixture at roomtemperature. The mixture is then brought to 40° C. with stirring for 24hours.

After returning to room temperature, 20 ml of diethyl ether are addedand cooling is carried out to 10° C. The mixture is then acidified by a5% by volume aqueous hydrochloric acid solution until a pH of 3 isobtained in the aqueous phase. 120 ml of diethyl ether are then added.10 g of pure sodium hydrogencarbonate are then added until a pH of 8 isobtained in the aqueous phase. The amine is then extracted by foursuccessive extractions, each with 60 ml of diethyl ether, and theorganic phase thus obtained is then dried with approximately 5 g ofanhydrous sodium sulphate. After filtration, the solvent is evaporatedon a rotary evaporator at 40° C. under 1 mbar and then using a vacuummanifold at room temperature under 0.2 mbar. 19.36 g of diethyl2,2-dimethyl-1-(1,1-dimethylethylamino)propylphosphonate were thusobtained. The NMR characteristics of this product are as follows:

¹H NMR in CDCl₃:

0.99 ppm (s, 9H, t-Bu),

1.06 ppm (s, 9H, t-Bu),

1.28 ppm (t, 6H, J_(H-H)=7.1 Hz, CH₃),

2.69 ppm (d, 1H, J_(H-P)=17.9 Hz, H in the position α to P),

4.06 ppm (broad unresolved peak, 4H, J_(H-H)=7.1 Hz, CH₂)

¹³C NMR in CDCl₃:

16.49 ppm (d, J_(C-P)=5.5 Hz, CH ₃—CH₂),

27.90 ppm (d, J_(C-P)=6.1 Hz, CH ₃—C—C),

30.74 ppm (s, CH ₃—C—N),

35.24 ppm (d, J_(C-P)=9.6 Hz, CH₃—C—C),

50.93 ppm (s, CH₃—C—N),

59.42 ppm (d, J_(C-P)=132.9 Hz, CH),

61.39 ppm (d, J_(C-P)=7.1 Hz, CH ₂).

³¹P NMR in CDCl₃:

29.84 ppm.

b) Synthesis of Tert-butyl 1-diethylphosphono-2,2-dimethylpropylNitroxide

2.28 g (0.0082 mol) of the amine prepared in a) are dissolved in 5 ml ofdichloromethane at room temperature and the solution thus obtained isthen introduced into a round-bottomed flask which has been cooled to 0°C. and is equipped with a magnetic stirrer. A solution of 1.29 g (0.0075mol) of metachloroperbenzoic acid (MCPBA) in 5 ml of dichloromethane isadded dropwise. After stirring for 6 hours at room temperature, asaturated aqueous NaHCO₃ solution is added to the mixture until CO₂elution has ceased, i.e. approximately 30 ml of this solution. Theorganic phase is recovered and dried with approximately 5 g of sodiumsulphate. The solvent is then removed on a rotary evaporator at 40° C.under 1 mbar and then using a vacuum manifold at room temperature under0.2 mbar. 1.39 g of an orange oil are thus obtained. This oil ispurified on a column with a diameter of 4 cm and a height of 30 cmcontaining 100 g of silica (silica gel 60, particle size 0.040-0.063 mm)by carrying out the following procedure: A suspension is preparedcomprising the 100 g of silica mixed with 200 ml of an eluent consistingof a CH₂ _(Cl) ₂/THF/pentane mixture in the proportions by volume of1/1/2. The column is filled with this suspension and, after having beenallowed to stand for one hour, the 1.39 g of orange oil are thendeposited at the top of the column in the form of an 80 % solution byvolume in the eluent. At least 200 ml of eluent are necessary to purifythe product. The liquid at the foot of the column is recovered in 15 mlfractions. The volatile species are then removed, first of all on arotary evaporator at 40° C. to a residual pressure of 1 mbar and thenusing a vacuum manifold at room temperature under 0.2 mbar. 1.06 g oftert-butyl 1-diethylphosphono-2,2-dimethylpropyl nitroxide are finallycollected, the expanded formula of which is:

The elemental analysis of the final product is in accordance with thecalculated values. The EPR data for this product are as follows:

a_(P)=45.26 G

a_(N)=14.27 G

g=2.0061 (Landé factor)

This radical is stable insofar as its EPR spectrum does not show anysubstantial modification after storage for two months at 25° C.

For reasons of simplicity, this product is known as β-P.

EXAMPLE 2

a) Synthesis of the magnesium compound (CH₃)₂CH—MgBr

1 g (0.041 mol) of magnesium turnings, covered with 10 ml of diethylether, and then one crystal (approximately 5 mg) of iodine, the functionof the latter being to activate the magnesium and to initiate thereaction, are placed in a 250 ml, round-bottomed, two-necked flaskequipped with a magnetic stirrer and a reflux condenser comprising adrying tube filled with CaCl₂.

5.04 g of isopropyl bromide (0.041 mol), diluted in 10 ml of diethylether, are then added dropwise via a dropping funnel. The mixture isleft stirring at room temperature for 3 hours.

b) Preparation of Tert-butyl 1-phenyl-2-methylpropyl Nitroxide

0.3 g of phenyl N-tert-butylnitrone (PBN), i.e. 0.0017 mol, in solutionin 5 ml of diethyl ether, is placed in a 100 ml, round-bottomed,two-necked flask equipped with a magnetic stirrer and a reflux condenserand purged with nitrogen. The solution of the magnesium compoundprepared in a) is then run in dropwise. 10 ml of distilled water arethen added and the mixture is left stirring at room temperature for 2hours. Extraction is then carried out with 2 times 20 ml of diethylether and the organic phase is then dried with 5 g of sodium sulphate.After filtration, the volatile species are removed from the organicsolution using a rotary evaporator at 40° C. to 1 mbar and then using avacuum manifold at room temperature under 0.2 mbar. 0.42 g of anorange-yellow liquid is thus obtained. Purification is then carried outon silica in a way identical to that described in Example 1b), exceptthat the eluent is a pentane/acetone mixture in a ratio by volume of90/10. After evaporation of the eluent in the same way as in Example1b), 0.1 g of tert-butyl 1-phenyl-2-methylpropyl nitroxide is collected,the expanded formula of which is:

The elemental analysis of the final product is in accordance with thecalculated values. The EPR data for this product are as follows:

a_(N)=15.21 G

a_(N)=3.01 G.

This radical is stable insofar as its EPR spectrum does not show anysubstantial modification after storage for two months at 25° C. Forreasons of simplicity, this product is known as β-ø.

EXAMPLES 3 TO 16

150 g of styrene, y millimol of initiator and x millimol of stable freeradical are introduced at 20° C. and under a nitrogen atmosphere into a0.25 liter stainless steel reactor equipped with a ribbon agitator and atemperature control. The whole system is brought to a temperature T (°C.). The point at which the mixture reaches the temperature T is definedas the starting point of the test.

Samples are then withdrawn in the course of time for analysis:

of the conversion to polymer (“conv” in the tables), which correspondsto the percentage by weight of solid obtained after evaporation under avacuum of 25 mbars for 20 minutes at 200° C. of the sample withdrawnwith respect to its initial weight;

of the weight-average molecular mass (Mw) and number-average molecularmass (Mn) and therefore of the polydispersity P which is equal to Mw/Mn,these determinations being carried out by gel permeation chromatography.

The results are combined in Tables 1 and 2 as a function of the natureand amounts x and y respectively of stable free radical and of initiatorintroduced. Tables 1 and 2 give the change in Mn, in conversion and inpolydispersity as a function of the duration of polymerization,calculating from the starting point. Examples 10 to 16 are comparative.

Example No. 3 4 5 6 7 8 9 Stable Nature β-P β-P β-P β-P β-P β-P β- freeAmount x 9.42 1.53 1.53 0.75 1.09 5.78 9.55 radical (millimol) InitiatorNature Benz. Benz. Benz. Benz. AIBN AIBN Benz. Per. Per. Per. Per. Per.Amount y 3.76 0.62 0.62 0.31 0.91 2.74 3.8 (millimol) T (° C.) 125 125110 110 95 95 125 Mn 1 h 40 min. 9,700 53,000 30,600 39,000 34,700 6,6008,300 3 h 30 min. 15,000 69,000 47,600 70,000 44,100 9,400 11,100 7 h19,800 107,000 87,000 105,000 58,400 12,900 14,400 20 h 126,800 22,200Conv. 1 h 40 min. 35 33.8 17.5 17 14 10.4 25 (%) 3 h 30 min. 52.8 50.630 26.5 17.7 20.2 44 7 h 70.2 78.5 51 45 28.4 30 60 20 h 61.6 53 P 1 h40 min. 1.13 1.35 1.15 1.2 1.64 1.33 1.14 3 h 30 min. 1.18 1.53 1.181.39 1.50 1.27 1.11 7 h 1.17 1.47 1.38 1.52 1.43 1.25 1.10 20 h 1.591.14

Comparative Example No. 10 11 12 13 14 15 16 Stable Nature Tempo TempoTempo Tempo Tempo DTBN free Amount x 21.8 3.72 1.34 0.77 21.8 9.24radical (millimol) Initiator Nature Benz. Benz. Benz. Benz. Benz. Benz.Benz. Per. Per. Per. Per. Per. Per. Per. Amount y 16.94 2.85 1.03 0.6216.94 16.94 3.71 (millimol) T (° C.) 125 125 125 125 110 125 125 Mn 1 h40 min. 18,500 33,500 17,000 3 h 30 min. 7 h 36,900 33,000 66,500 4,50020 h 3,300 Conv. 1 h 40 min. 19 23 0 72 0 (%) 3 h 30 min. 0 0 7 h 51.857 61 0 9 20 h 16 0 P 1 h 40 min. 1.62 2.8 3 h 30 min. 7 h 1.49 1.421.53 1.17 20 h 1.32

What is claimed is:
 1. Process for the polymerization orcopolymerization of at least one monomer by the radical route in thepresence of a stable free radical comprising a sequence of formula

in which the monovalent R_(L) radical has a molar mass greater than 15,wherein the process results in polymers or copolymers with aweight-average molecular mass greater than 10,000 gram/mol and thedegree of conversion of monomer to polymer or copolymer is greater than50%.
 2. Process according to claim 1, characterized in that R_(L) has amolar mass greater than
 30. 3. Process according to claim 2,characterized in that R_(L) has a molar mass of between 40 and
 450. 4.Process according to claim 1, characterized in that the remainingvalencies of the carbon atom and of the nitrogen atom of the formula (1)are bonded to monovalent radicals.
 5. Process according to claim 1,characterized in that R_(L) comprises a phosphoryl group.
 6. Processaccording to claim 5, characterized in that R_(L) is represented by theformula

in which R¹ and R² ₁ which can be identical or different, are chosenfrom halogens or alkyl, cycloalkyl, alkoxy, aryloxy, aryl, aralkyloxy,perfluoroalkyl or aralkyl radicals.
 7. Process according to claim 6,characterized in that R¹ and R² comprise from one to 20 carbon atoms. 8.Process according to claim 1, characterized in that R_(L) comprises atleast one aromatic ring.
 9. Process according to claim 8, characterizedin that R_(L) is a phenyl radical.
 10. Process according to claim 1,characterized in that the stable free radical is tert-butyl1-diethylphosphono-2,2-dimethylpropyl nitroxide.
 11. Process accordingto claim 9, characterized in that the stable free radical is tert-butyl1-phenyl-2-methylpropyl nitroxide.
 12. Process according to claim 1,characterized in that the stable free radical is present in theproportion of 0.005% to 5% by weight of the sum of the mass ofpolymerizable monomer and of stable free radical.
 13. Process accordingto claim 1, characterized in that a free-radical initiator is present.14. Process according to claim 13, characterized in that thefree-radical initiator is present in the proportion of 50 to 50,000 ppmbased on the mass of polymerizable monomer.
 15. Process according toclaim 1, characterized in that it results in polymers or copolymers witha weight-average molecular mass ranging from 100,000 gram/mol to 400,000gram/mol measured by gel permeation chromatography.
 16. Processaccording to claim 1, characterized in that at least one polymerizablemonomer is vinylaromatic.
 17. Process according to claim 16,characterized in that at least one vinylaromatic monomer is styrene. 18.Process according to claim 1, characterized in that the temperature isbetween 90 and 120° C.
 19. Process according to claim 18, characterizedin that the temperature is between 100 and 120° C.
 20. Process accordingto claim 1, characterized in that the temperature is between 120 and200° C.
 21. Process according to claim 15, wherein the stable freeradical is present in the proportion of 0.005% to 5% by weight of thesum of the mass of the monomer and of the stable free radical andwherein a free-radical initiator is present in the proportion of 50 to50,000 ppm based on the mass of the monomer.
 22. Process according toclaim 21, wherein the R_(L) has a molar mass of between 40 and
 450. 23.Process according to claim 22, wherein the remaining valencies of thecarbon atom and of the nitrogen atom of the formula (1) are bonded tomonovalent radicals.
 24. Process for the polymerization orcopolymerization of at least one monomer by the radical route in thepresence of a stable free radical comprising a sequence of formula

in which the monovalent R_(L) has a molar mass greater than 15 andcomprises a phosphoryl group.
 25. Process according to claim 24, whereinthe process results in polymers or copolymers with a weight-averagemolecular mass greater than 10,000 gram/mol and the degree of conversionof monomer to polymer or copolymer is greater than 50%.
 26. Processaccording to claim 25, wherein the process results in polymers orcopolymers with a weight-average molecular mass ranging from 100,000gram/mol to 400,000 gram/mol.
 27. Process according to claim 26, whereinthe stable free radical is present in the proportion of 0.005% to 5% byweight of the sum of the mass of the monomer and of the stable freeradical and wherein a free-radical initiator is present in theproportion of 50 to 50,000 ppm based on the mass of the monomer. 28.Process according to claim 27, wherein the R_(L) has a molar mass ofbetween 40 and
 450. 29. Process according to claim 28, wherein theremaining valencies of the carbon atom and of the nitrogen atom of theformula (1) are bonded to monovalent radicals.
 30. Process for thepolymerization or copolymerization of at least one monomer by theradical route in the presence of a stable free radical comprising asequence of formula

in which the monovalent R_(L) has a molar mass greater than 15, whereina hydrogen atom is bonded to the carbon atom of the sequence. 31.Process according to claim 30, wherein the process results in polymersor copolymers with a weight-average molecular mass greater than 10,000gram/mol and the degree of conversion of monomer to polymer or copolymeris greater than 50%.
 32. Process according to claim 31, wherein theprocess results in polymers or copolymers with a weight-averagemolecular mass ranging from 100,000 gram/mol to 400,000 gram/mol. 33.Process according to claim 32, wherein the stable free radical ispresent in the proportion of 0.005% to 5% by weight of the sum of themass of the monomer and of the stable free radical and wherein afree-radical initiator is present in the proportion of 50 to 50,000 ppmbased on the mass of the monomer.
 34. Process according to claim 33,wherein the R_(L) has a molar mass of between 40 and
 450. 35. Processaccording to claim 34, wherein the remaining valencies of the carbonatom and of the nitrogen atom of the formula (1) are bonded tomonovalent radicals.
 36. Process according to claim 2, wherein theremaining valencies of the carbon atom and of the nitrogen atom of theformula (1) are bonded to monovalent radicals.
 37. Process according toclaim 36, wherein the temperature is between 100 and 120° C.
 38. Processaccording to claim 36, wherein the temperature is between 120 and 200°C.
 39. Process according to claim 24, wherein the remaining valencies ofthe carbon atom and of the nitrogen atom of the formula (1) are bondedto monovalent radicals.
 40. Process according to claim 39, wherein thetemperature is between 100 and 120° C.
 41. Process according to claim39, wherein the temperature is between 120 and 200° C.
 42. Processaccording to claim 35, wherein the temperature is between 100 and 120°C.
 43. Process according to claim 35, wherein the temperature is between20 and 200° C.